Reduction in the fluid liquid and blood volume.
Step-by-step explanation:
During space travel, the volume of fluid liquid in the body is reduced. Also the volume of blood is also decreased by 22% . Because of this there will be only less blood in the body to pup to all the organs .
This lack of blood leads to atrophy.Also due to the gravitational force liquids and blood flows in the downward direction. That will cause dizziness or fainting. It may also lead to other ill effects. If the gravitational force is low or absent than fluids will flow in upward direction.